Solid-state imaging device and electronic apparatus

ABSTRACT

A solid-state imaging device includes: a light-receiving element; and a multilayer film which is disposed on a side of a light-receiving surface of the light-receiving element and is formed by laminating a plurality of layers made of materials having different refractive indices, in which a defect layer is included in at least one of the laminated layers, wherein in the defect layer, a plurality of kinds of materials having different refractive indices coexist in a surface parallel to the light-receiving surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device that isused as an imaging device and an electronic apparatus having thesolid-state imaging device mounted thereon.

2. Description of the Related Art

In solid-state imaging devices represented by CMOS (Complementary MetalOxide Semiconductor) sensors, organic materials are generally used asthe materials of color filters for achieving color separation. This isbecause organic materials provide a high degree of freedom forabsorption spectral characteristic design and make it easy to obtaincharacteristics close to those desired.

However, the use of organic materials may result in a great increase incost and even insufficient durability in view of temperaturecharacteristics and light stability. Moreover, the processes that can beused for the upper layers of the organic material layer are limited. Forexample, it is very difficult to form microstructures that have atransmittance-improving effect on the upper layers of the color filter.

For these and other reasons, the use of an inorganic multilayer film inthe color filters of a solid-state imaging device has been proposed (seethe Pamphlet of WO2005/069376, for example).

SUMMARY OF THE INVENTION

To achieve color separation in a solid-state imaging device, it isnecessary to obtain different optical characteristics for three colors(RGB) in each pixel. In the related-art technique described inWO2005/069376, when color separation is achieved using an inorganicmultilayer film, the different optical characteristics for three colorsare obtained by changing the height (thickness) of a layer (defectlayer) having a different center thickness in the inorganic multilayerfilm.

However, in the configuration where the different opticalcharacteristics for three colors are obtained by changing thethicknesses of the defect layers in the inorganic multilayer film,portions disposed on the upper layer side of the defect layers have sucha shape that each pixel has a step. For this reason, there is concernthat the amount of light transmitting through the inorganic multilayerfilm may decrease due to a bulge of the step portions.

It is therefore desirable to provide a solid-state imaging device and anelectronic apparatus in which even when color separation is achievedusing a multilayer film, the multilayer film does not have a steppedshape but has a uniform thickness for each pixel, thus providing goodoptical characteristics.

According to an embodiment of the present invention, there is provided asolid-state imaging device including: a light-receiving element; and amultilayer film which is disposed on a side of a light-receiving surfaceof the light-receiving element and is formed by laminating a pluralityof layers made of materials having different refractive indices, inwhich a defect layer is included in at least one of the laminatedlayers, in which in the defect layer, a plurality of kinds of materialshaving different refractive indices coexist in a surface parallel to thelight-receiving surface.

In the solid-state imaging device having the above-mentionedconfiguration, the refractive index in the defect layer depends on theratio of areas of the materials coexisting in the surface. That is tosay, by changing the area ratio (duty ratio) of the materials in thesurface, a desired wavelength of light is allowed to pass through themultilayer film. Therefore, the multilayer film can be formed into auniform thickness regardless of the wavelength of light to betransmitted.

In the embodiment of the present invention, even when a multilayer filmin which a plurality of layers made of different materials are laminatedis used as a color filter for achieving color separation, the multilayerfilm has a uniform thickness and will not have a stepped shape in eachpixel. Therefore, it is possible to prevent the amount of transmittedlight from decreasing due to a bulge of the step portions. That is tosay, according to the embodiment of the present invention, it ispossible to obtain good optical characteristics for the multilayer filmused as a color filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view showing an exemplary basic configurationof a solid-state imaging device.

FIG. 2 is a plan view showing a specific example of a two-dimensionalarrangement of an OCCF.

FIG. 3 is a sectional side view showing an exemplary specificconfiguration of the OCCF according to an embodiment of the presentinvention.

FIGS. 4A to 4C are diagrams showing a specific example of a pattern thatis symmetrical in two orthogonal directions.

FIGS. 5A to 5C are diagrams showing an overview of diffraction optics inthe sub-wavelength domain.

FIG. 6 is a diagram showing an overview of a resonance domain.

FIG. 7 is a graph showing an example of the results obtained by plottingthe relationship between respective items described based on FIGS. 5A to5C and FIG. 6.

FIG. 8 is a graph showing a specific example of a change in transmissioncharacteristics when the area ratio (duty ratio) of a checker pattern ischanged.

FIGS. 9A to 9F are sectional side views showing a specific example of amanufacturing method of the OCCF according to the embodiment of thepresent invention.

FIG. 10 is a graph showing a specific example of reflection/transmissioncharacteristics when there is no defect layer in which a relation(refractive index difference Δn)=(high refractive index nh)−(lowrefractive index nl)=1 is satisfied (i.e., the thickness of the defectlayer is λ/4).

FIG. 11 is a sectional side view showing another exemplary specificconfiguration of the OCCF according to the embodiment of the presentinvention.

FIG. 12 is a diagram showing a specific example of the relationshipbetween a laminated structure that forms a multilayer film and anincidence angle.

FIG. 13 is a sectional side view showing another exemplary specificconfiguration of the OCCF according to the embodiment of the presentinvention.

FIG. 14 is a block diagram showing an exemplary configuration of animaging apparatus which is an example of an electronic apparatusaccording to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, modes for carrying out the present invention (hereinafterreferred to as embodiments) will be described. The description will begiven in the following order.

1. Exemplary Basic Configuration of Solid-State Imaging Device;

2. First Embodiment (Exemplary Configuration and Manufacturing Method);

3. Second Embodiment;

4. Third Embodiment; and

5. Exemplary Configuration of Electronic Apparatus

1. Exemplary Basic Configuration of Solid-State Imaging Device

FIG. 1 is a sectional side view showing an exemplary basic configurationof a solid-state imaging device.

The solid-state imaging device shown in FIG. 1 is one that is widelyknown as a CMOS sensor, for example, and a plurality of light-receivingelements 1 are arranged in a surface of a semiconductor substrate thatis not shown. Each of the light-receiving elements 1 corresponds to onepixel. Each light-receiving element 1 is covered with an interlayerinsulating film 2 made of a light-transmitting material, and multilayerwirings 3 are arranged in the interlayer insulating film 2. Moreover, onthe interlayer insulating film 2, namely on a side of a light-receivingsurface of the light-receiving element 1, a planarization process isperformed by CMP (Chemical Mechanical Polishing), for example, and anon-chip color filter (OCCF) 4 that transmits only a specific colorcomponent of light is disposed. On the OCCF 4, an on-chip microlens(OCL) 5 for focusing an incident light on each of the light-receivingelements 1 is disposed.

FIG. 2 is a plan view showing a specific example of a two-dimensionalarrangement of an OCCF.

The OCCF 4 is configured to separate a different color component foreach pixel. Specifically, as shown in FIG. 2, the OCCF 4 is arranged ina so-called Bayer arrangement in which a row of repeated R (red) and G(green) pixels and a subsequent row of repeated G and B (blue) pixelsappear so as to correspond to respective pixels that are arrangedtwo-dimensionally in a matrix form.

2. First Embodiment

Next, a main characteristic part of the solid-state imaging deviceaccording to an embodiment of the present invention will be described.

In this section, the OCCF 4 will be described in detail as the maincharacteristic part of the solid-state imaging device.

Exemplary Configuration

FIG. 3 is a sectional side view showing an exemplary specificconfiguration of the OCCF according to the embodiment of the presentinvention.

The OCCF 4 shown in FIG. 3 is formed of a multilayer film in which aplurality of layers made of materials having different refractiveindices is laminated. As the materials having different refractiveindices, inorganic materials can be used. This is because inorganicmaterials are advantageous over organic materials in view of cost,durability, degree of freedom in process choice, and the like.Specifically, examples of the plurality of inorganic materials havingdifferent refractive indices include silicon dioxide (SiO₂) having a lowrefractive index and titanium dioxide (TiO₂) having a high refractiveindex. A multilayer film in which layers of these materials arelaminated is typically called a dielectric multilayer film, and in thisspecification, will be simply called “multilayer film”. The laminationdirection of the solid-state imaging device is the same as thelamination direction of the multilayer film.

Moreover, the multilayer film that constitutes the OCCF 4 includes atleast one defect layer 11 having a different center thickness in thelaminated layers.

Therefore, the multilayer film that constitutes the OCCF 4 has alaminated structure in which two layers of TiO₂ layers 12, 13, 14, and15 and SiO₂ layers 16, 17, 18, and 19 are repeatedly laminated in apredetermined order above and below the defect layer 11. That is to say,because of the characteristics necessary for a solid-state imagingdevice, the laminated structure of the multilayer film includes 9 layersin total composed of a periodic structure of each four layers 12 to 19disposed above and below the defect layer 11. In this case, the TiO₂layers 12, 13, 14, and 15 and the SiO₂ layers 16, 17, 18, and 19 may beconfigured to have an optical thickness of λ/4. Here, the opticalthickness is a value nd that is obtained by multiplying the refractiveindex n of the material of the layer by the thickness d of the layer. Inaddition, λ is the wavelength of light that is transmitted through theOCCF 4.

The defect layer 11 has a configuration such that a plurality of kindsof materials having different refractive indices coexist in a surfaceparallel to the light-receiving surface of the light-receiving element1. The plurality of kinds of materials having different refractiveindices may be SiO₂ having a low refractive index and TiO₂ having a highrefractive index. That is to say, the same formation materials as thoseused for the other layers 12 to 19 of the multilayer film other than thedefect layer 11 may be used. Therefore, in the defect layer 11, TiO₂portions 11 a and SiO₂ portions 11 b coexist. In this case, the TiO₂portions 11 a and the SiO₂ portions 11 b are arranged so that theycoexist in a regular pattern.

However, the arrangement pattern of the TiO₂ portions 11 a and the SiO₂portions 11 b is symmetrical in two orthogonal directions in thesurface. Here, the arrangement pattern that is symmetrical in twoorthogonal directions implies that the same pattern is obtained evenwhen the pattern is rotated by 90° in the surface.

FIGS. 4A to 4C are diagrams showing a specific example of a pattern thatis symmetrical in two orthogonal directions.

The pattern that is symmetrical in two directions may be a so-calledchecker pattern in which the TiO₂ portions 11 a and the SiO₂ portions 11b are alternately arranged in a checkered pattern as shown in FIG. 4A.The example shown in FIG. 4A shows a checker pattern in which the ratioof areas of the portions 11 a and 11 b is 0.5.

The arrangement pattern of the TiO₂ portions 11 a and the SiO₂ portions11 b is not particularly limited to the checker pattern. That is to say,as long as the same pattern is obtained even when the pattern is rotatedby 90° in the surface, an equiangular rectangular pattern as shown inFIG. 4B or a concentric pattern as shown in FIG. 4C may be used, forexample.

Moreover, in the arrangement pattern of the TiO₂ portions 11 a and theSiO₂ portions 11 b, the ratio of areas of the portions 11 a and 11 b isset based on the wavelength of light reaching the light-receivingelement. Here, the “ratio of areas” mentioned above refers to the ratioof the area of the TiO₂ portions 11 a to the area of the SiO₂ portions11 b coexisting in a predetermined region (for example, one pixelregion) of the surface. Hereinafter, the ratio of areas will be simplyreferred to as “area ratio” or “duty ratio”. That is to say, since thedefect layer has a microstructure that uses TiO₂ and SiO₂ which areexamples of a plurality of kinds of materials having differentrefractive indices, by changing the area ratio (duty ratio) of therespective materials in the surface, a desired wavelength of light isallowed to pass therethrough. Therefore, when the plurality oflight-receiving elements 1 are arranged so as to correspond to differentcolors, respectively, the duty ratio of the TiO₂ portions 11 a and theSiO₂ portions 11 b will be different for each pixel.

In the microstructure that uses TiO₂ and SiO₂ which are examples of theplurality of kinds of materials having different refractive indices, itis known that the microstructure exhibits a refractive index given byFormula 4 below when the microstructure is sufficiently smaller than thewavelength of light. Here, the derivation process of Formula 4 will bedescribed in brief.

FIGS. 5A to 5C are diagrams showing an overview of diffraction optics inthe sub-wavelength domain. When a beam having a certain wavelength isincident on a diffractive grating having a periodic structure,high-order light is output in addition to the 0th-order beam as shown inFIG. 5A. However, when the period of the periodic structure decreases tobe the same or smaller than the wavelength of an incident beam, thediffraction condition for high-order light is no longer valid.Therefore, the output beam will be substantially composed of the0th-order beam. The phase of the 0th-order beam depends on theparameters of the 0th-order grating, and the value of the phase can bechanged within a certain range (Effective Media Theory). An example willbe described by way of a structural birefringent portion formed of aplurality of concavo-convex portions, as shown in FIG. 5B. When thepitch of the concavo-convex portions of the structural birefringentportion is decreased to be smaller than the wavelength of transmittedlight, a refractive index relative to a TM-polarized light and arefractive index relative to a TE-polarized light may have differentvalues. Thus, the structural birefringent portion has propertiesequivalent to those of a birefringent material. Specifically, when theconcavo-convex pitches c and d and the refractive indices n1 and n2 aredefined as shown in FIG. 5C, the refractive index n_(TE) relative to theTE-polarized light, the refractive index n_(TM) relative to theTM-polarized light, and the relationship between these refractiveindices can be expressed by Formulas 1, 2, and 3 below. These formulasare known in the related art.

$\begin{matrix}{{\overset{\_}{n}}_{TE} = \sqrt{{fn}_{1}^{2} + {\left( {1 - f} \right)n_{2}^{2}}}} & (1) \\{{\overset{\_}{n}}_{TM} = \frac{1}{\sqrt{{f/n_{1}^{2}} + {\left( {1 - f} \right)/n_{2}^{2}}}}} & (2) \\{{\overset{\_}{n}}_{TE} > {\overset{\_}{n}}_{TM}} & (3)\end{matrix}$

FIG. 6 is a diagram showing an overview of a resonance domain. In theresonance domain, it is necessary to regard light as electromagneticwaves. That is, light is regarded as vector waves. Specifically, in theresonance domain, propagation of light in a grating layer is calculatedby solving the Maxwell equation. Moreover, as shown in FIG. 6, theboundary condition at the boundary of homogeneous media must besatisfied. For this reason, in the resonance domain, propagation oflight greatly depends on polarization, and a very small change inoptical constant may result in a great characteristic change. This isknown in the related art.

FIG. 7 is a graph showing an example of the results obtained by plottingthe relationship between respective items described based on FIGS. 5A to5C and FIG. 6. In the drawing, the line A represents a refractive indexwhen an electric field is parallel to a groove, and the line Brepresents a refractive index when the electric field is perpendicularto the groove.

When the TiO₂ portions 11 a and the SiO₂ portions 11 b are arranged in achecker pattern, the defect layer 11 has a refractive index (the line C)that is intermediate of those of the lines A and B. That is to say, itcan be seen that in the case of the checker pattern, the duty ratio andthe effective refractive index of the respective materials have anapproximately proportional value.

Therefore, the refractive index for the checker pattern can beapproximated by Formula 4 below if the high refractive index nh is 2.5,the low refractive index nl is 1.5, and the duty ratio is d.

n _(—) eff≈nl·d+nh·(1−d)  (4)

FIG. 8 is a graph showing a specific example of a change in transmissioncharacteristics when the area ratio (duty ratio) of a checker pattern ischanged.

FIG. 8 shows the calculation results of a change in the transmissioncharacteristics using a FDTD (finite-difference time-domain) method whenthe duty ratios are R:1.0, G:0.5, and B:0, respectively. In the graph,10000 corresponds to transmittance of 1.

To obtain such a change in the transmission characteristics as shown inFIG. 8, because of the characteristics necessary for a solid-stateimaging device, the OCCF 4 preferably has a configuration such that thelaminated structure of the multilayer film includes 9 layers in total (aperiodic structure composed of each four layers disposed above and belowthe defect layer 11), and the thickness of the defect layer 11 is ½ ofthe wavelength λ of blue light.

Manufacturing Method

FIGS. 9A to 9F are sectional side views showing a specific example of amanufacturing method of the OCCF according to the embodiment of thepresent invention.

The OCCF can be manufactured by the following method.

First, as shown in FIG. 9A, a SiO₂ layer 16, a TiO₂ layer 12, a SiO₂layer 17, and a TiO₂ layer 13 which are disposed in the lower part ofthe multilayer film are formed in that order by a MOCVD (Metal OrganicChemical Vapor Deposition) method, for example. Moreover, a SiO₂ portion11 b that constitutes the defect layer 11 is laminated on the entire topsurface of the TiO₂ layer 13. At that time, it is preferable to laminatea low refractive-index material for the purpose of manufacturing.

After that, as shown in FIG. 9B, a mask pattern for forming amicrostructure of the defect layer 11 is placed on the SiO₂ portion 11b, and a microstructure pattern is transferred to a resist 21 byphotolithography or an electron beam drawing method.

Then, as shown in FIG. 9C, the transferred microstructure pattern istransferred to the SiO₂ portion 11 b by performing a dry etching such asRIE (Reactive Ion Etching), for example.

Subsequently, as shown in FIG. 9D, TiO₂ which is another material thatconstitutes the defect layer 11 is deposited using a MOCVD method, forexample, so as to cover the SiO₂ portion 11 b in which themicrostructure pattern is transferred, thus burying a groove shape inthe SiO₂ portion 11 b. At that time, it is preferable to laminate a highrefractive-index material for the purpose of manufacturing.

After that, as shown in FIG. 9E, a planarization process based on a CMP(Chemical Mechanical Polishing), for example, is performed on a topsurface side of the deposited TiO₂ layer 22. This is because theconcave-convex shape based on the microstructure pattern is alsotransferred to the top surface side of the TiO₂ layer 22. By thisplanarization process, the defect layer 11 in which the pattern of theTiO₂ portions 11 a and the SiO₂ portions 11 b is arranged and the TiO₂layer 14 covering the top surface side of the defect layer 11 areformed.

After the planarization process is completed, as shown in FIG. 9F, aSiO₂ layer 18, a TiO₂ layer 15, and a SiO₂ layer 19 which are disposedon the upper part of the multilayer film are formed in that order on theTiO₂ layer 14 by a MOCVD method, for example.

By the above-mentioned processes, an OCCF 4 having a configuration shownin FIG. 3 is manufactured.

As described above, in the OCCF 4 of the solid-state imaging deviceaccording to the present embodiment, a plurality of kinds of materialshaving different refractive indices are arranged so as to coexist in asurface parallel to the light-receiving surface of the light-receivingelement 1, thus forming the defect layer 11. For this reason, therefractive index of the defect layer 11 depends on the ratio of areas ofthe respective materials that coexist in a regular pattern. That is tosay, by changing the area ratio (duty ratio) of the respective materialsin the surface, a desired wavelength of light is allowed to passtherethrough. Therefore, even when different optical characteristics areobtained for each pixel, it is not necessary to change the thickness ofthe defect layer 11 from pixel to pixel.

More specifically, the OCCF 4 of the solid-state imaging deviceaccording to the present embodiment has a configuration such that theratio of areas of the TiO₂ portions 11 a and the SiO₂ portions 11 bwhich are arranged in a regular pattern in the defect layer 11 is setbased on the wavelength of light reaching the light-receiving element 1.That is to say, when the plurality of light-receiving elements 1 arearranged so as to correspond to different colors, respectively, anddifferent optical characteristics are obtained for each pixel, it isonly necessary to change the duty ratio of the TiO₂ portions 11 a andthe SiO₂ portions 11 b in the defect layer 11 for each pixel. Therefore,even when different optical characteristics are obtained for each pixel,it is not necessary to change the thickness of the defect layer 11 frompixel to pixel. That is to say, even when the colors of adjacent pixelregions in the Bayer arrangement are different, it is not necessary tochange the thickness (height) of the defect layer 11 for each pixel.

As seen above, according to the present embodiment, even when amultilayer film in which inorganic material layers are laminated is usedas the OCCF 4 for achieving color separation, the multilayer film has auniform thickness and will not have a stepped shape in each pixel. Thatis to say, it is possible to eliminate a non-effective region resultingfrom steps which appear in each pixel in the related art, and to form areliable surface so as to have a uniform thickness. Therefore, it ispossible to prevent the amount of transmitted light from decreasing dueto a bulge of the step portions.

In addition, in the OCCF 4 according to the present embodiment, the TiO₂portions 11 a and the SiO₂ portions 11 b which constitute the defectlayer 11 coexist in the surface parallel to the light-receiving surfaceof the light-receiving element 1 symmetrically in two orthogonaldirections. That is to say, the arrangement pattern of the TiO₂ portions11 a and the SiO₂ portions 11 b is symmetrical in two orthogonaldirections in the surface. Therefore, by arranging the respectivematerials constituting the defect layer 11 in a regular pattern, it ispossible to eliminate the effect of polarization components included inan incident light. That is to say, by eliminating polarizationdependence, it is possible to prevent the transmittance from beingdifferent due to polarization components.

From these advantages, according to the present embodiment, it ispossible to obtain good optical characteristics for the multilayer filmused as the OCCF 4. That is to say, even when color separation isachieved using an inorganic multilayer film, the inorganic multilayerfilm does not have a stepped shape but has a uniform thickness for eachpixel, whereby good optical characteristics can be obtained.

In the OCCF 4 described in the present embodiment, SiO₂ and TiO₂ areused as the plurality of inorganic materials constituting the multilayerfilm. Moreover, SiO₂ and TiO₂ are used as the plurality of kinds ofmaterials constituting the defect layer 11 in the multilayer film. Thatis to say, the respective materials are composed of two materials whichhave a refractive index difference of 1 or more. The reason for usingsuch materials is based on the following facts.

FIG. 10 is a graph showing a specific example of reflection/transmissioncharacteristics when there is no defect layer in which a relation(refractive index difference Δn)=(high refractive index nh)−(lowrefractive index nl)=1 is satisfied (i.e., the thickness of the defectlayer is λ/4).

The OCCF 4 of a solid-state imaging device is necessary to providereflection characteristics of 800 or more with respect to blue light(wavelength: 450 nm) and red light (wavelength: 600 nm), for example, sothat light incident to a certain color filter does not transmit throughother color filters of other colors. For this reason, a refractive indexdifference (Δn=nh−nl) of 1 or more is necessary.

Therefore, the plurality of inorganic materials that constitute themultilayer film and the plurality of kinds of materials having differentrefractive indices that constitute the defect layer 11 are preferablycomposed of two materials which have a refractive index difference of 1or more.

Although in the present embodiment, TiO₂ (refractive index nh=2.5) andSiO₂ (refractive index nl=1.5) are exemplified as the two materialshaving a refractive index difference of 1 or more, the materials thatcan be used are not limited to these materials.

Moreover, in the OCCF 4 described in the present embodiment, thelaminated structure constituting the multilayer film has such astructure that two layers made of a plurality of inorganic materials arelaminated above and below the defect layer 11. That is to say, thelaminated structure of the multilayer film includes 9 layers in totalthat are composed of a laminated structure in which the respectivelayers 12 to 19 are repeatedly and sequentially arranged above and belowthe defect layer 11. Therefore, even when a multilayer film made ofinorganic materials is used as the OCCF 4 of a solid-state imagingdevice, it is possible to provide optical characteristics necessary forthe OCCF 4.

3. Second Embodiment

Next, another exemplary configuration of a main part of the solid-stateimaging device according to an embodiment of the present invention willbe described.

In this section, only the difference from the first embodiment will bedescribed.

FIG. 11 is a sectional side view showing another exemplary specificconfiguration of the OCCF according to the embodiment of the presentinvention.

The OCCF 4 shown in FIG. 11 has the defect layer 11 which is differentfrom that of the first embodiment described above.

In the defect layer 11 according to the present embodiment, the ratio ofareas of the respective portions 11 a and 11 b in the regular pattern ofthe TiO₂ portions 11 a and the SiO₂ portions 11 b constituting thedefect layer 11 is different at respective positions which correspond tothe plurality of light-receiving elements 1 arranged in the surface.That is to say, the area ratio (duty ratio) of the TiO₂ portions 11 aand the SiO₂ portions 11 b is different for each pixel region.

More specifically, the duty ratio of the TiO₂ portions 11 a and the SiO₂portions 11 b is different at different positions which are respectivelylocated closer to a central portion and a periphery of an effectiveimaging region that is formed by each of the plurality oflight-receiving elements 1.

This is because in a solid-state imaging device, the incidence angle oflight tends to incline as the light is incident to positions closer tothe periphery of an effective imaging region. That is to say, in orderto cope with the inclination of the incidence angle at the periphery ofthe effective imaging region, it is necessary to change the opticalcharacteristics (specifically, transmittance or a refractive index) inthe defect layer 11 so as to be different at positions which are locatedcloser to the central portion and the periphery of the effective imagingregion even when the effective imaging region corresponds to the samecolor, for example.

Therefore, in the arrangement pattern of the TiO₂ portions 11 a and theSiO₂ portions 11 b in the defect layer 11, the area ratio of the TiO₂portions 11 a and the SiO₂ portions 11 b is changed so that a higherrefractive index is obtained at the periphery of the effective imagingregion than at the central portion, for example.

FIG. 12 is a diagram showing a specific example of the relationshipbetween a laminated structure that forms a multilayer film and anincidence angle.

The refractive index n_eff and the thickness h of the defect layer 11relative to light at an incidence angle θ can be expressed by Formulas 5and 6 below.

n _(—) eff·h·cos θ=λ/2  (5)

cos θ=λ/[2·h·{nl·d+nh·(1−d)}]  (6)

The incidence angle θ of light is determined by optical components suchas lenses that are used together with a solid-state imaging device.Therefore, when the incidence angle θ of light is determined, therefractive index n_eff or the thickness h of the defect layer 11 can bedetermined by Formula 5 or 6.

However, according to a technique that changes the thickness h of thedefect layer 11 based on the incidence angle θ, it is very difficult todetermine the thickness reliably. Moreover, steps may be formed in themultilayer film due to a change in thickness h.

For this reason, in the present embodiment, the refractive index n_effof the defect layer 11, namely the area ratio of the TiO₂ portions 11 aand the SiO₂ portions 11 b is changed based on the incidence angle θ oflight while maintaining the thickness h to be uniform.

As described above, in the OCCF 4 of the solid-state imaging deviceaccording to the present embodiment, the ratio of areas of the TiO₂portions 11 a and the SiO₂ portions 11 b in the defect layer 11 isdifferent at different positions which are respectively located closerto the central portion and the periphery of the effective imaging regionthat is formed by the light-receiving element 1. Therefore, it ispossible to prevent a decrease in transmittance at the periphery whilecoping with the inclination of the incidence angle at the periphery ofthe effective imaging region. That is to say, it is possible toefficiently cope with the inclination of the incidence angle of light atthe periphery of the effective imaging region in the solid-state imagingdevice.

4. Third Embodiment

Next, another exemplary configuration of a main part of the solid-stateimaging device according to an embodiment of the present invention willbe described.

In this section, only the difference from the first or second embodimentwill be described.

FIG. 13 is a sectional side view showing another exemplary specificconfiguration of the OCCF according to the embodiment of the presentinvention.

The OCCF 4 shown in FIG. 13 has the defect layer 11 which is differentfrom that of the first or second embodiment.

In the defect layer 11 according to the present embodiment, the ratio ofareas of the TiO₂ portions 11 a and the SiO₂ portions 11 b constitutingthe defect layer 11 is different at different positions which arerespectively located closer to the central portion and the periphery ofa region corresponding to one light-receiving element 1. That is to say,the area ratio (duty ratio) of the TiO₂ portions 11 a and the SiO₂portions 11 b which are arranged in a regular pattern is different atdifferent positions which are respectively located closer to the centralportion and the periphery of one pixel region formed by each of thelight-receiving elements 1. Here, the area ratio refers to the ratio ofthe area of the TiO₂ portions 11 a and the area of the SiO₂ portions 11b that coexist in each sub-divided region when one pixel region isdivided into a plurality of the sub-divided regions.

This is because light being transmitted through the defect layer 11 hasalso been transmitted through the OCL 5, even in one pixel region, theincidence angle of light tends to incline as the light becomes incidentto positions closer to the periphery of the pixel region. That is tosay, in order to cope with the inclination of the incidence angle at theperiphery of the pixel region, it is necessary to change the opticalcharacteristics (specifically, transmittance or a refractive index) inthe defect layer 11 so as to be different at positions which are locatedcloser to the central portion and the periphery of the pixel region evenin the same pixel region, for example.

Therefore, in the TiO₂ portions 11 a and the SiO₂ portions 11 b in onepixel region, the duty ratio of the TiO₂ portions 11 a and the SiO₂portions 11 b is changed so that a higher refractive index is obtainedat the periphery of the pixel region than at the central portion, forexample.

The relationship between the incidence angle θ of light and therefractive index n_eff of the defect layer 11 is the same as that in thesecond embodiment described above.

Moreover, the relationship with other pixel regions is maintaineduniformly similar to that described in the first embodiment. That is tosay, the distribution density of the TiO₂ portions 11 a and the SiO₂portions 11 b is uniformly changed in each pixel region. However, asdescribed in the second embodiment, the distribution density may bechanged for each pixel region. That is to say, the duty ratio of theTiO₂ portions 11 a and the SiO₂ portions 11 b may be changed for eachpixel region, while changing the duty ratio of the TiO₂ portions 11 aand the SiO₂ portions 11 b in each of the pixel regions.

As described above, in the OCCF 4 of the solid-state imaging deviceaccording to the present embodiment, the distribution density of theTiO₂ portions 11 a and the SiO₂ portions 11 b in the defect layer 11 isdifferent at different positions which are respectively located closerto the central portion and the periphery of one pixel region. Therefore,it is possible to prevent a decrease in transmittance at the peripheryeven when the incidence angle of light is inclined at the periphery ofone pixel region after the light passes through the OCL 5. That is tosay, it is possible to efficiently cope with the inclination of theincidence angle of light at the periphery of one pixel region.

5. Exemplary Configuration of Electronic Apparatus

The present invention is not limited to application in a solid-stateimaging device but can be applied to an electronic apparatus such as animaging apparatus. Here, the electronic apparatus may be an imagingapparatus (camera system) such as a digital camera or a video camera, ora mobile apparatus such as a cellular phone or a PDA (Personal DigitalAssistant) having an imaging function. Moreover, the imaging apparatusmay be configured in a form of modules that are mounted on theelectronic apparatus, namely a camera module.

Imaging Apparatus

FIG. 14 is a block diagram showing an exemplary configuration of animaging apparatus which is an example of an electronic apparatusaccording to the embodiment of the present invention.

As shown in FIG. 14, an imaging apparatus 100 according to theembodiment of the present invention includes an optical system includinga lens array 101 and the like, an imaging device 102, a DSP circuit 103which is a camera signal processing unit, a frame memory 104, a displaydevice 105, a recording device 106, a manipulation system 107, a powersource system 108, and the like. Moreover, the DSP circuit 103, theframe memory 104, the display device 105, the recording device 106, themanipulation system 107, and the power source system 108 are connectedto each other via a bus line 109.

The lens array 101 captures an incident light (image light) from asubject to be focused on an imaging surface of the imaging device 102.

The imaging device 102 converts the amount of incident light focused onthe imaging surface by the lens array 101 to electrical signals for eachpixel and outputs the electrical signals as pixel signals. As theimaging device 102, the solid-state imaging device according to theembodiments described above is used.

The display device 105 is configured by a panel display device such as aliquid-crystal display device or an organic EL (Electro Luminescence)display device and displays moving pictures or still images that areimaged by the imaging device 102.

The recording device 106 records the moving pictures or the still imagesimaged by the imaging device 102 on a recording medium such as a videotape or a DVD (Digital Versatile Disk).

The manipulation system 107 issues manipulation instructions related tovarious functions of the imaging apparatus under the control of a user.

The power source system 108 appropriately supplies various power sourceswhich function as operation power sources for the DSP circuit 103, theframe memory 104, the display device 105, the recording device 106, andthe manipulation system 107 to these supply targets.

Such an imaging apparatus 100 is applied to a video camera or a digitalcamera, and a camera module for mobile apparatuses such as cellularphones. Since the solid-state imaging device according to theembodiments described above is used as the imaging device 102 of theimaging apparatus 100, the solid-state imaging device is able to obtaingood optical characteristics, and thus an electronic apparatus havingexcellent image quality can be provided. Moreover, since it is possibleto easily cope with miniaturization of a pixel size, high-resolutionimages resulting from an increased number of pixels can be obtained.

Although specific preferred embodiments of the present invention havebeen described and illustrated in the embodiments described above, thepresent invention is not limited to above contents.

For example, the formation materials, dimensions, and the like of theconstituent elements of the solid-state imaging device described andillustrated in the respective embodiments are only illustrations ofexamples of concretization at the time of carrying out the presentinvention. That is, it should be understood that the technical scope ofthe present invention is not limited to these examples.

Therefore, the present invention is not limited to the contentsdescribed in the respective embodiments but can be appropriatelymodified without departing from the spirit of the present invention.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2009-098612 filedin the Japan Patent Office on Apr. 15, 2009, the entire contents ofwhich is hereby incorporated by reference.

1. A solid-state imaging device comprising: a light-receiving element;and a multilayer film which is disposed on a side of a light-receivingsurface of the light-receiving element and is formed by laminating aplurality of layers made of materials having different refractiveindices, in which a defect layer is included in at least one of thelaminated layers, wherein in the defect layer, a plurality of kinds ofmaterials having different refractive indices coexist in a surfaceparallel to the light-receiving surface.
 2. The solid-state imagingdevice according to claim 1, wherein the plurality of materials thatconstitute the multilayer film are inorganic materials.
 3. Thesolid-state imaging device according to claim 1, wherein in the defectlayer, the plurality of kinds of materials having different refractiveindices coexist in the surface symmetrically in two orthogonaldirections.
 4. The solid-state imaging device according to claim 1,wherein in the defect layer, the ratio of areas of the materialscoexisting in the surface is set based on the wavelength of lightreaching the light-receiving element.
 5. The solid-state imaging deviceaccording to claim 4, wherein a plurality of the light-receivingelements are arranged on the surface; and in the defect layer, the ratioof areas of the materials is different at respective positions whichcorrespond to the respective light-receiving elements.
 6. Thesolid-state imaging device according to claim 4, wherein in the defectlayer, the ratio of areas of the materials is different at differentpositions which are respectively located closer to a central portion anda periphery of an effective imaging region that is formed by each of thelight-receiving elements.
 7. The solid-state imaging device according toclaim 4, wherein in the defect layer, the ratio of areas of thematerials is different at different positions which are respectivelylocated closer to a central portion and a periphery of one pixel regionthat is formed by each of the light-receiving elements.
 8. Thesolid-state imaging device according to claim 1, wherein the pluralityof materials that constitute the multilayer film and the plurality ofkinds of materials having different refractive indices that constitutethe defect layer are composed of two materials which have a refractiveindex difference of 1 or more.
 9. The solid-state imaging deviceaccording to claim 1, wherein the multilayer film has a laminatedstructure in which two layers made of the plurality of materials arelaminated above and below the defect layer.
 10. An electronic apparatushaving a solid-state imaging device mounted thereon, the solid-stateimaging device comprising: a light-receiving element; and a multilayerfilm which is disposed on a side of a light-receiving surface of thelight-receiving element and is formed by laminating a plurality oflayers made of materials having different refractive indices, in which adefect layer is included in at least one of the laminated layers,wherein in the defect layer, a plurality of kinds of materials havingdifferent refractive indices coexist in a surface parallel to thelight-receiving surface.